Frequently Asked Questions

EnerKíte is among the first teams to successfully automate the control of kites. We are experts in all the ciritcal disciplines of this technology. This advantage is secured by the Know-How of the shareholders and patent applications. According to measurements obtained by the Fraunhofer IWES, EnerKíte already has the most powerful technology today - with quite a margin. The new wing technology and drive configuration result in an unrivalled safety and efficiency of our products, starting already at a power output of 100 kW. This enables products with short amortisation period, a fast break-even and a timely introduction into a market of dynamic growth. Experience and profits in this market secure the subsequent scaling and market penetration. Investors can expect a high return of investment at a minimised risk..

EnerKíte wings are flying perpendicular to the oncoming wind with high speed and generate lift. By means of the tethers, the high aerodynamic forces arrive at the generator winch on the ground. The tethers are reeled-off the winch and the generator converts the torque and winch velocity into electrical energy. At the end of the tether, the wing is brought into a retractable state. The aerodynamic forces are low and the winch acts for a short time as a motor to reel in the tether. When the cycle starts again, the energy gained during the traction phase surpasses significantly the small energy lost during retraction.

The connection is analogous to a Surfkite with three tethers. Using these three lines the change in angle of attack and the control of turns is realised. A sophisticated system of sensors captures all relevant forces, positions, velocities and the orientation of the wing. The control software calculates all necessary commands, constrains the power and torques and monitors the correct operation of all components

With an operational altitude of approximately 300 m EnerKítes slightly surpass the tips of current wind turbine blades. Using appropriate markings, EnerKítes are recognizable for low-flying aircraft during day and night.

Airspace monitoring techniques, such as a passive radar technology, will enable the cost-efficient detection of air traffic in the future. The system reacts to possible air traffic and initiates an evasive manoeuvre towards a low altitude. This will render optical marking redundant.

EnerKítes reach higher altitudes than the towers of current wind turbines, at a fraction of the used material, and the area swept by the wings is variable and larger. This enables high and more constant yield at relatively low cost, even at low wind speeds. The tethers transfer the aerodynamic forces to the ground and enable significantly smaller foundations. This drastically reduces the infrastructure demands, especially off-shore, and enables mobile or transportable systems.

According to sonic measurements of the Reiner Lemoine Institute, the demonstration unit already complies with current limits. Future wings will operate with less connection lines, lower airspeed and a higher distance to the ground and hence should result in significantly lower sound emissions. The nacelle is located at the ground and does not radiate noise to the same extent as the nacelle of conventional wind turbines.

According to a 2007 NABU study even conventional wind turbines are not a significant danger to birds. A collision with birds has not been observed during several hundred flight hours with the demonstration unit. Compared to the blade tips of wind turbines EnerKíte wings fly considerably slower, which helps the birds to evade. There is no warm nacelle in the air, which attracts insects and hence their predators. Habitats and environmental concerns will be considered during site selection, of course.

Bats fly at altitudes of 30 - 50 m and, using echolocation, are not as responsive to the movement of wind turbines blades as birds. The negative pressure behind the fast turbine blade tips may lead to barotrauma. With higher altitudes and lower movement speeds, EnerKítes are a considerably lower risk to bats.

In case of wind speeds below 2-3 m/s at an altitude of 200 - 500 m, the ultra-light wings can be held aloft using special manoeuvres using power input from the ground. For longer periods of low wind conditions, the wing is landed automatically.

The demonstration unit has been operated during rain, snow and hail. Rain drips off the wing surface, just as it does drip off a tent canvas. Constant change in movement and slight vibrations of the flexible material make massive ice accretion unlikely. Hence the danger of falling ice seems significantly lower compared to conventional wind turbines.

Squalls and strong winds are no concern for the wing, the surface area is relatively small and during extreme gusts the wing can move with the wind be releasing the tether. In case of forecasted severe weather, like hurricanes and thunderstorms, the EnerKíte wings can be landed and sheltered, if necessary.

Approximately 5 lightning strikes per year are registered for conventional wind turbines at, for example, Northern Germany. Not all wind turbines comply with the lightning protection class 1, as required for IEC, and 4 - 8% of wind turbines are damaged due to lightning strikes. At high altitudes the probability of lightning strikes would be even higher. If EnerKítes are landed, however, the risk of lightning strike drops to less than one hundredth compared to wind turbines. Lightning protection on the ground is realised easily, and an early warning system is currently developed.

A telescopic mast system enables the fully-automatic take-off and landing. With sufficient wind speeds, the wing can simply dock to and from the mast. During lower wind speeds the mast and the wing at the tip of the mast is put in rotation. The wing establishes a stable circular path with a defined airspeed and the tether is extended and retracted to land the wing or to take off.

Mechanical and thermic stresses, humidity and UV radiation causes plastics to age. The supporting structure of our patented wings is industrially manufactured from high-performance plastics and ensures high efficiency and durability. Similar to the covers of sails and hang gliders, the covers of the support structure can last several years and easily serviced and maintained. Stress-oriented and damage-tolerant design, protective coatings and defined maintenance intervals ensure the efficiency of the material over the complete life cycle of the system.

The functional and structural safety of the systems is comparable to the those of aircraft. Redundant systems ensures the safety of the machine even in case of failures. The ageing of the structure is monitored and subject to preventative maintenance. Using three tethers and an immediate drop in aerodynamic force in case of any single tether failure, a completely untethered wing is ruled out. The winch uses two independent motors, where each one is able to safely bring the wing to the landing mast. One should keep in mind that the ultra-light wings are built with a density comparable to that of Styrofoam.

Until the scaling and development of MW class EnerKítes is completed, portable systems with 100 kW rated power will access the on shore niche markets. Temporary renewable energy production on dump and landfill sites, at the edge of remote construction sites, renewable emergency power supply and humanitarian aid operations are just a few examples.

EnerKítes will be distanced at 100 m or more for bigger systems and longer tether lengths. The take-off and landing is the dimensioning factor, as well as the envelope of the flight trajectory. Precise control of the individual kites can eliminate mutual obstruction, since they are all aware of each others states. By means of a wide spacial utilisation of the airspace, especially with respect to altitude, the shadowing effects are decreased. At larger systems, we assume a considerably better space utilisation with respect to the yield compared to conventional wind turbines.

Future large-scale systems will not only have lower manufacturing costs but also increase in specific yield. In comparison to small-scale wind turbines, which are quite expensive compared to utility scale systems, this will already be true for small series productions.

Mobile systems with 100 kW rated power and wing surface areas of up to 100 m² combined with a battery or with a grid connection can be timely realised. The product development should be finished by 2017. In 2018 first pilot systems will be operating. In 2021 the small-batch series production and the scaling towards MW-class systems will follow. For additional information please contact This email address is being protected from spambots. You need JavaScript enabled to view it..

Is EnerKíte available for cooperation with or as a supplier for companies or institutes?

Yes. We assume that the airborne wind energy technology will require a comprehensive development. It seems neither sensible nor expedient that every start-up and player in this field tackles all challenges alone. With our commercial background and expertise we strive for fully-functional and reliable products and prototypes in the development of avionics, sensors, controls and ground stations. This enables a reliable operation and a focus on individual strengths and concepts.

For the purpose of strategic, long-term and trustful partnerships we offer cooperation in the scope of an intelligent and modern research and development network.

The EnerKíte ground station is available for flight tests and technology development.